1. Field of the Invention
The present invention relates to a stereo camera unit in which a camera unit body having a pair of video cameras is mounted at a predetermined position on a mount section.
2. Description of the Related Art
As a three-dimensional measuring technique using images, so-called stereoscopic image processing is known. In stereoscopic image processing, a pair of images of a target are taken by right and left video cameras (stereo cameras) from different positions, and correlation between the taken images is found. The distance between the stereo cameras and the target is found from the parallax with respect to the same object according to the principle of triangulation using preset parameters, for example, the distance (camera base length) between light-receiving surfaces of image sensors, such as CCDs (charge coupled devices), provided in the video cameras and the focal length.
In this stereoscopic image processing, two image signals obtained from the stereo cameras are superimposed while being sequentially shifted, and the position where the two image signals coincide is found.
The accuracy of the distance measured by stereoscopy depends on the accuracy of the mounting positions of the video cameras, more specifically, the positional accuracy between the light-receiving surfaces. When the light-receiving surfaces of the right and left video cameras are displaced, the camera base length changes, and this causes error between the measured distance and the actual distance. Similarly, tilting of the light-receiving surface of each video camera also reduces the measurement accuracy.
For this reason, the camera base length is defined by fixing the right and left video cameras at positions in the camera unit body that ensure the preset camera base length.
However, even when the camera base length between the video cameras is accurately defined, if the mount position of the camera unit body is displaced by crossing of a bolt and a screw hole when the camera unit body is fixed only by the screw, translational displacement in the up-down direction and rotational direction occurs to the video cameras.
As measures against the above problem, the present applicant discloses a technique of ensuring the positional accuracy between both video cameras (Japanese Unexamined Patent Application Publication No. 2001-88623). In this technique, pins protrude at two positions in the center of a chassis (camera unit body), fitting holes in which the pins are fitted are provided in a front rail (mount section) of the vehicle, and the positional accuracy between the video cameras is ensured by fitting the pins in the fitting holes.
In this publication, a spacer is provided between the chassis and the front rail, and the pins are fitted in the fitting holes through the spacer. Therefore, by adjusting the thickness and so on of the spacer, the camera unit body can be accurately mounted without any influence of inclination of the chassis that differs among the types of vehicles.
In the technique disclosed in the above publication, when the camera unit body is mounted to the mount section, it is positioned by fitting the pins protruding from the camera unit body into the fitting holes provided in the mount section. Therefore, when the positions of the fitting holes in the front rail are changed, the positions of the pins protruding from the chassis also need to be changed.
However, if the positions of the pins protruding from the camera unit body are changed in accordance with the positions of the fitting holes in the mount section, it is necessary to prepare a camera unit body for each type of mount section. This makes parts sharing difficult, and lacks versatility.
Further, when a camera unit body is prepared for each type of the mount section, parts management becomes troublesome, and management cost increases.